Moisture cured reactive hot melt adhesive with monofunctional reactants as grafting agents

ABSTRACT

High green strength reactive hot melt adhesives are prepared using crystalline monofunctional reactants.

FIELD OF THE INVENTION

The invention relates to hot melt adhesives, in particular reactive hotmelt adhesives having improved set speed and green strength.

BACKGROUND OF THE INVENTION

Hot melt adhesives are solid at room temperature but, upon applicationof heat, melt to a liquid or fluid state in which form they are appliedto a substrate. On cooling, the adhesive regains its solid form. Thehard phase(s) formed upon cooling the adhesive imparts all of thecohesion (strength, toughness, creep and heat resistance) to the finaladhesive. Curable hot melt adhesives, which are also applied in moltenform, cool to solidify and subsequently cure by a chemical crosslinkingreaction. An advantage of hot melt curable adhesives over traditionalliquid curing adhesives is their ability to provide “green strength”upon cooling prior to cure.

The majority of reactive hot melts are moisture-curing urethaneadhesives. These adhesives consist primarily of isocyanate terminatedpolyurethane prepolymers that react with surface or ambient moisture inorder to chain-extend, forming a new polyurethane polymer. Polyurethaneprepolymers are conventionally obtained by reacting diols withdiisocyanates. Pure diols are favored for use, instead of polyols withhigher functionality, to avoid excessive branching that can lead to poorpot stability. Methylene bisphenyl diisocyanate (MDI) is favored overlower molecular weight isocyanates to minimize volatility. Cure isobtained through the diffusion of moisture from the atmosphere or thesubstrates into the adhesive, and subsequent reaction. The reaction ofmoisture with residual isocyanate forms carbamic acid. This acid isunstable, decomposing into an amine and carbon dioxide. The amine reactsrapidly with isocyanate to form a urea. The final adhesive product is acrosslinked material held together primarily through urea groups andurethane groups.

The prior art discloses that the performance of reactive hot meltadhesives for most applications may be substantially improved by theincorporation of acrylic polymers into conventional polyurethaneadhesives, in particular reactive hydroxy-containing and non-reactiveacrylic copolymers. Improvement in green strength may be obtained byadding higher molecular weight polymers (reactive or not) and/orincorporating crystalline diols, most commonly polyester diols.

These prior art adhesives are extremely tough, with outstanding lowtemperature flexibility, heat and chemical resistance and specificadhesion to polar substrates. Adhesion to a wide range of othersubstrates may be obtained through the addition of adhesion promoterssuch as silane coupling agents. Despite these advances in the art, thereremains a need for improvements in reactive hot melt technology toexpand the application of such adhesives and their effectiveness in suchapplications. The present invention addresses this need.

SUMMARY OF THE INVENTION

The invention provides moisture curable reactive hot melt adhesivecompositions that have improved set speed and green strength.

One aspect of the invention is directed to a moisture curable hot meltadhesive composition comprising a multifunctional polyisocyanate, atleast one or more polymeric diols or triols, a polymeric ornon-polymeric crystalline monofunctional reactant, and at least onefunctional or non-functional thermoplastic.

Another embodiment of the invention is directed to a method of improvingthe set speed and green strength of a hot melt adhesive comprisingadding an effective amount of a monofunctional reactant to a reactivehot melt adhesive formulation.

Yet another embodiment of the invention is directed to a method forbonding materials together which comprises applying the reactive hotmelt adhesive composition of the invention in a liquid form to a firstsubstrate, bringing a second substrate in contact with the compositionapplied to the first substrate, and subjecting the applied compositionto conditions which will allow the composition to cool and cure to anirreversible solid form, said conditions comprising moisture.

Still another aspect of the invention is directed to an article ofmanufacture comprising the adhesive of the invention.

DETAILED DESCRIPTION OF THE INVENTION

All percents are percent by weight of the adhesive composition, unlessotherwise stated.

It has now been discovered that high green strength reactive hot meltadhesives may be prepared using any functional group that is capable ofreacting with isocyanate. The adhesives of the invention have good greenstrength and maintain fast setting and crosslinkability.

The moisture curable, hot melt polyurethane adhesives of the inventionmay be prepared through the reaction of a mixture of non-polymeric orpolymeric monofunctional reactants, with a multifunctionalpolyisocyanate-containing compound, one or more polymeric diols ortriols, and preferably, a thermoplastic polymer, at a temperature offrom about 120° F. to about 275° F. The adhesives of the inventioncomprise an multifunctional polyisocyanate, MDI being preferred, fromabout 0.1 to about 30 wt % and preferably from about 5 to about 20 wt %of a monofunctional reactant, and from about 0 to about 90 wt % andpreferably from about 5 to about 80 wt % and most preferably from about10 to about 70 wt % of a polyester polyol, and from about 0 to about 80wt % and preferably from about 5 to about 80 wt % and most preferablyfrom about 10 to about 70 wt % of a polyether polyol.

To obtain the adhesive of the invention, various monofunctionalreactants that are capable of reacting with isocyanate, such ashydroxyl, carboxyl, thiol, amine, mercapto and amides may be utilized,whether polymeric or non-polymeric. One preferred reactant is lowmolecular weight linear polyethylene monoalcohols, commerciallyavailable as UNILIN from Baker Petrolites. These materials have meltingpoints ranging from about 60° C. to about 110° C. By partially reactingthe monoalcohols with the polyisocyanate end group of the polyurethaneprepolymers, a hot melt that is able to crosslink under moisture isobtained. Upon cooling from the melt, the setting of the shortpolyethylene segments at the end of the prepolymer freezes the movementof the entire chain, resulting in the setting of the hot melt adhesive.As a result, the formulation is fast setting even without crystallinepolymers, including polyester diols, which are not necessary for theformulation. Another preferred reactant ispolyethylene-block-polyethylene glycol, commercially available asUNITHOX (Baker Petrolites). As with the monoalcohol reactant, thepolymer based tail would generate green strength, but the uncapped—NCOend would still be available for curing and forming a crosslinkedpolyurethane network. A still further preferred embodiment arering-opened polyesters and polyamides that are monofunctional.

The reactive hot melt compositions formed with the monofunctionalreactant have a unique architecture as opposed to standard reactive hotmelt compositions. The architecture of such reactive hot melts is a longflexible middle chain as the backbone of polyurethane. The backboneshould be no less than 400 in Mn, and preferably in the range of about1000–25000. Various components, such as polyol, PEG, PPG,hydroxyl-terminated Poly BD, polycaprolactone, polyTHF, copolymersthereof or other functionalized polymers. Monofunctional reactants thatcan react with isocyanate, such as hydroxyl, carboxyl, thiol, amine,mercapto and amides may be utilized. The end groups, and properties ofthe reactive hot melt adhesive, will vary depending upon the materialutilized.

The reactive hot melt compositions of the invention are useful forbonding articles composed of a wide variety of substrates (materials),including but not limited to wood, metal, polymeric plastics, glass andtextiles. As such, these adhesives find particular use in applicationssuch as use in water towers, for bonding to exterior surfaces, bondingto wood with high levels of pitch and e.g., in marine and automotiveapplications. Other non-limiting uses include textile bondingapplications (carpet and clothing), use in the manufacture of footwear(shoes), use as a glazing/backbedding compound in the manufacture ofwindows, use in the manufacture of doors including entry doors, garagedoors and the like, use in the manufacture of architectural panels, usein bonding components on the exterior of vehicles, and the like.

The urethane prepolymers that can be used to prepare the adhesives ofthe invention are those conventionally used in the production ofpolyurethane hot melt adhesive compositions. Any suitable compound,which contains two or more isocyanate groups, may be used for preparingthe urethane prepolymers. Typically from about 2 to about 25 parts byweight of an isocyanate is used.

Organic polyisocyanates, which may be used to practice the invention,include alkylene diisocyanates, cycloalkylene diisocyanates, aromaticdiisocyanates and aliphatic-aromatic diisocyanates. Specific examples ofsuitable isocyanate-containing compounds include, but are not limitedto, ethylene diisocyanate, ethylidene diisocyanate, propylenediisocyanate, butylene diisocyanate, trimethylene diisocyanate,hexamethylene diisocyanate, toluene diisocyanate,cyclopentylene-1,3-diisocyanate, cyclo-hexylene-1,4-diisocyanate,cyclohexylene-1,2-diisocyanate, 4,4′-diphenylmethane diisocyanate,2,2-diphenylpropane-4,4′-diisocyanate, xylylene diisocyanate,1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, m-phenylenediisocyanate, p-phenylene diisocyanate, diphenyl-4,4-diisocyanate,azobenzene-4,4′-diisocyanate, diphenylsulphone-4,4′-diisocyanate,2,4-tolylene diisocyanate, dichlorohexa-methylene diisocyanate,furfurylidene diisocyanate, 1-chlorobenzene-2,4-diisocyanate,4,4′,4″-triisocyanatotriphenylmethane, 1,3,5-triisocyanato-benzene,2,4,6-triisocyanato-toluene,4,4′-dimethyldiphenyl-methane-2,2′,5,5-tetratetraisocyanate, and thelike. While such compounds are commercially available, methods forsynthesizing such compounds are well known in the art. Preferredisocyanate-containing compounds are methylenebisphenyldiisocyanate(MDI), isophoronediisocyanate (IPDI), hydrogenatedmethylenebisphenyldiisocyanate (HMDI) and toluene diisocyanate (TDI).

Most commonly, the prepolymer is prepared by the polymerization of apolyisocyanate with a polyol, most preferably the polymerization of adiisocyanate with a diol. The polyols used include polyhydroxy ethers(substituted or unsubstituted polyalkylene ether glycols or polyhydroxypolyalkylene ethers), polyhydroxy polyesters, the ethylene or propyleneoxide adducts of polyols and the monosubstituted esters of glycerol, aswell as mixtures thereof. The polyol is typically used in an amount ofbetween about 10 to about 70 parts by weight.

Preferably the adhesive is prepared by including a thermoplasticpolymer. The thermoplastic polymer may be either a functional or anon-functional thermoplastic. Suitable thermoplastic polymers includeacrylic polymers, functional acrylic polymers, non-functional acyrlicpolymers, hydroxy functional acrylic polymers, polyvinyl acetate,polyvinyl chloride, methylene, polyvinyl ether, cellulose, acetate,styrene acrylonitrile, amorphous polyolefin, thermoplastic urethane,polyacrylonitrile, polybutadiene diol, isobutylene diol and mixturesthereof.

Examples of polyether polyols include a linear and/or branched polyetherhaving plural numbers of ether bondings and at least two hydroxylgroups, and contain substantially no functional group other than thehydroxyl groups. Examples of the polyether polyol may includepolyoxyalkylene polyol such as polyethylene glycol, polypropyleneglycol, polybutylene glycol and the like. Further, a homopolymer and acopolymer of the polyoxyalkylene polyols may also be employed.Particularly preferable copolymers of the polyoxyalkylene polyols mayinclude an adduct at least one compound selected from the groupconsisting of ethylene glycol, propylene glycol, diethylene glycol,dipropylene glycol, triethylene glycol, 2-ethylhexanediol-1,3,glycerin,1,2,6-hexane triol, trimethylol propane, trimethylol ethane,tris(hydroxyphenyl)propane, triethanolamine, triisopropanolamine,ethylenediamine and ethanolamine; with at least one compound selectedfrom the group consisting of ethylene oxide, propylene oxide andbutylene oxide.

A number of suitable polyols are commercially available. Non-limitingexamples include CP4701 (Dow Chemicals), Niax 11-34 (Union CarbideCorp), Desmorphen 3900 (Bayer), Propylan M12 (Lankro Chemicals),Highflex 303 (Daiichi Kogyo Seiyaku K.K.) and Daltocel T 32-75 (ICI).“Polymer polyols” are also suitable, i.e., graft polyols containing aproportion of a vinyl monomer, polymerized in situ, e.g., Niax 34-28.

Polyester polyols are formed from the condensation of one or morepolyhydric alcohols having from 2 to 15 carbon atoms with one or morepolycarboxylic acids having from 2 to 14 carbon atoms. Examples ofsuitable polyhydric alcohols include ethylene glycol, propylene glycolsuch as 1,2-propylene glycol and 1,3-propylene glycol, glycerol,pentaerythritol, trimethylolpropane, 1,4,6-octanetriol, butanediol,pentanediol, hexanediol, dodecanediol, octanediol, chloropentanediol,glycerol monallyl ether, glycerol monoethyl ether, diethylene glycol,2-ethylhexanediol-1,4,cyclohexanediol-1,4,1,2,6-hexanetriol,1,3,5-hexanetriol, 1,3-bis-(2-hydroxyethoxy)propane and the like.Examples of polycarboxylic acids include phthalic acid, isophthalicacid, terephthalic acid, tetrachlorophthalic acid, maleic acid,dodecylmaleic acid, octadecenylmaleic acid, fumaric acid, aconitic acid,trimellitic acid, tricarballylic acid, 3,3′-thiodipropionic acid,succinic acid, adipic acid, malonic acid, glutaric acid, pimelic acid,sebacic acid, cyclohexane-1,2-dicarboxylic acid,1,4-cyclohexadiene-1,2-dicarboxylic acid,3-methyl-3,5-cyclohexadiene-1,2-dicarboxylic acid and the correspondingacid anhydrides, acid chlorides and acid esters such as phthalicanhydride, phthaloyl chloride and the dimethyl ester of phthalic acid.Preferred polycarboxylic acids are the aliphatic and cycloaliphaticdicarboxylic acids containing no more than 14 carbon atoms and thearomatic dicarboxylic acids containing no more than 14 atoms.

Commercially available polyols which may be used in the practice of theinvention include polyethers such as ARCOL PPG 2025 (Bayer), PolyG 20-56(Arch) and Pluracol P-2010 (BASF), polyesters such as Dynacoll 7360(Creanova), Fomrez 66-32 (Crompton) and Rucoflex S-105-30 (Bayer) andpolybutadiene such as PolyBD R-45HTLO (Elf Atochem).

In addition, the urethane prepolymers may be prepared by the reaction ofa polyisocyanate with a polyamino or a polymercapto-containing compoundsuch as diamino polypropylene glycol or diamino polyethylene glycol orpolythioethers such as the condensation products of thiodiglycol eitheralone or in combination with other glycols such as ethylene glycol,1,2-propylene glycol or with other polyhydroxy compounds disclosedabove. In accordance with one embodiment of the invention, the hydroxylcontaining acrylic polymer may function as the polyol component, inwhich case, no additional polyol need be added to the reaction.

Further, small amounts of low molecular weight dihydroxy, diamino, oramino hydroxy compounds may be used such as saturated and unsaturatedglycols, e.g., ethylene glycol or condensates thereof such as diethyleneglycol, triethylene glycol, and the like; ethylene diamine,hexamethylene diamine and the like; ethanolamine, propanolamine,N-methyldiethanolamine and the like.

Virtually any ethylenically unsaturated monomer containing afunctionality averaging one may be utilized in the compositions of thepresent invention. Functional monomers include, without limitation acid,hydroxy, amine, isocyanate, and thio functional monomers. Hydroxylfunctionality is preferred and is described in detail herein.

Most commonly employed are hydroxyl substituted C₁ to C₁₂ esters ofacrylic and methacrylic acids including, but not limited to hydroxylsubstituted methyl acrylate, ethyl acrylate, n-butyl acrylate,2-ethylhexyl acrylate, isobutyl acrylate, n-propyl or iso-propylacrylate or the corresponding methacrylates. Mixtures of compatible(meth)acrylate monomers may also be used. Additional monomers that maybe used include the hydroxyl substituted vinyl esters (vinyl acetate andvinyl propionate), vinyl ethers, fumarates, maleates, styrene,acrylonitrile, thermoplastic urethanes, amorphous polyolefins, as wellas comonomers thereof.

These monomers may blended with other copolymerizable comonomers asformulated so as to have a wide range of Tg values, as between about−60° C. and 105° C., preferably 15° C. to 85° C. Suitable comonomersinclude the C₁ to C₁₂ esters of acrylic and methacrylic acids including,but not limited to methyl acrylate, ethyl acrylate, n-butyl acrylate,isobutyl acrylate, 2-ethylhexyl acrylate, n-propyl or iso-propylacrylate or the corresponding methacrylates. Mixtures of compatible(meth)acrylate monomers may also be used. Additional monomers that maybe used include the vinyl esters (vinyl acetate and vinyl propionate),vinyl ethers, fumarates, maleates, styrene, acrylonitrile, ethylene,etc. as well as comonomers thereof. The hydroxyl containing monomers maybe the same or different from the monomers used in the remainder of theacrylic polymerization. The particular monomers selected will depend, inlarge part, upon the end use for which the adhesives are intended. Thus,adhesives to be used in pressure sensitive applications or inapplications wherein adhesion to metal is required will be selected toobtain a lower Tg polymer than may be desired in non-pressure sensitiveapplications or those involving more easily bonded substrates.

When the adhesive is to be prepared utilizing monomeric materials, therespective monomers may be added to the polyols and polymerized thereinprior to formation of the prepolymer or may be added to the alreadyformed prepolymer and the acrylic polymerization subsequently performed.In the case of polyamino or polymercapto containing prepolymers, in-situvinylic polymerization must be performed only in the pre-formedprepolymer.

The hydroxyl containing ethylenically unsaturated monomer is polymerizedusing conventional free radical polymerization procedures to arelatively low molecular weight. For purposes of clarification, use ofthe term “low molecular weight” means number average molecular weightsin the range of approximately 1,000 to 50,000, preferred for use aremonomers having an average molecular weight in the range of from about5,000 to about 30,000. Molecular weight distribution is characterized byGel Permeation Chromatography using a PL Gel, Mixed 10 micron column, aShimadzu Model RID 6A Detector with a tetrahydrofuran carrier solvent ata flow rate of 1 milliliter per minute. The low molecular weight isobtained by carefully monitoring and controlling the reaction conditionsand, generally, by carrying out the reaction in the presence of a chaintransfer agent such as dodecyl mercaptan. Subsequent to thepolymerization of the ethylenically unsaturated monomer(s), thepolyisocyanate and any additional ingredients required for the urethaneprepolymer forming reaction are added and that reaction is carried outusing conventional condensation polymerization procedures. In thismanner, the resultant isocyanate terminated urethane prepolymer formsthe reactive curing hot melt adhesive described above which containsabout 2 to about 90% of the low molecular weight hydroxyl containingpolymer.

It is also possible to polymerize the low molecular weight polymer inthe presence of the already formed isocyanate terminated urethaneprepolymer. This method has the drawback of subjecting the prepolymer tounnecessary heating during the acrylic polymerization, heating thatmight result in branching, viscosity increase, depletion of neededisocyanate groups and possible gellation. Although these disadvantagesare subject to control, more stringent control of conditions is requiredas compared to polymerization in the non-isocyanate functional urethanecomponents. When the reaction is run in the polyol or othernon-isocyanate containing component, there is also the advantage oflower reaction viscosities and reduced exposure to isocyanate vaporsbecause of the lesser amount of heating required.

Optionally, the hydroxyl containing functionality may be introduced intothe adhesive in the form of pre-polymerized low molecular weighthydroxyl containing polymers. In the latter case, typical polymersinclude hydroxyl substituted butyl acrylate, hydroxylated butylacrylate/methyl methacrylate copolymers, hydroxylated ethylacrylate/methyl methacrylate copolymers, and the like. Preferredpolymers have a number average molecular weight of 5,000 to 30,000 and ahydroxyl number of 4 to 30. If used in the form of low molecular weightpolymers, the polymers may be blended with the polyol prior to reactionthereof with the isocyanate or they may be added directly to theisocyanate terminated prepolymer.

While the adhesives may be used directly as described above, if desiredthe adhesives of the present invention may also be formulated withconventional additives that are compatible with the composition. Suchadditives include plasticizers, compatible tackifiers, curing catalysts,dissociation catalysts, fillers, anti-oxidants, pigments, adhesionpromoters, stabilizers, aliphatic C₅-C₁₀ terpene oligomers and the like.Conventional additives that are compatible with a composition accordingto this invention may simply be determined by combining a potentialadditive with the composition and determining if they are compatible. Anadditive is compatible if it is homogenous within the product.Non-limited examples of suitable additives include, without limitation,rosin, rosin derivatives, rosin ester, aliphatic hydrocarbons, aromatichydrocarbons aromatically modified aliphatic hydrocarbons, terpenes,terpene phenol, modified terpene, high molecular weight hindered phenolsand multifunctional phenols such as sulfur and phosphorous-containingphenol, terpene oligomers, DMDEE, paraffin waxes, microcrystallinewaxes, castor oil and hydrogenated castor oil.

The reactive hot melt adhesives of the invention may also contain flameretardant components. Fire retardant additives known in the art forimparting flame resistance to polyurethane compositions may be added.Such compounds include inorganic compounds such as a boron compound,aluminum hydroxide, antimony trioxide and the like, and other halogencompounds including halogen-containing phosphate compounds such astris(chloroethyl)phosphate, tris(2,3-dichloropropyl)-phosphate, and thelike. These and other flame retarding compositions are described in U.S.Pat. Nos. 3,773,695 4,266,042, 4,585,806, 4,587,273 and 4,849,467, andEuropean Patent No. 0 587 942. In a preferred embodiment,ethylenebistetrabromophthalimide and/ortris(2,3-dibromopropyl)-isocyanurate is added as a prime flame retardantcomponent. The ethylenebistetrabromophthalimide and/ortris(2,3-dibromopropyl)isocyanurate may be used with or without otherflame retardants. The composition may further comprise a chlorinatedparaffin and/or an aryl phosphate ester as a further flame retardantcomponent. The optional chlorinated paraffin imparts flame retardancy aswell as performing as a viscosity modifier. The aryl phosphate esterfurther imparts improved adhesion to the substrates. The flame retardantpolyurethane-based reactive hot melt adhesives when used in the practiceof the invention gives excellent flame retardancy while maintaining thetargeted properties of the base polymer, such as good green strength,controlled setting speed and good thermal stability at elevatedtemperatures.

The invention also provides a method for bonding articles together whichcomprises applying the reactive hot melt adhesive composition of theinvention in a liquid melt form to a first article, bringing a secondarticle in contact with the composition applied to the first article,and subjecting the applied composition to conditions which will allowthe composition to cool and cure to a composition having an irreversiblesolid form, said conditions comprising moisture. The composition istypically distributed and stored in its solid form, and is stored in theabsence of moisture. When the composition is ready for use, the solid isheated and melted prior to application. Thus, this invention includesreactive polyurethane hot melt adhesive compositions in both its solidform, as it is typically to be stored and distributed, and its liquidform, after it has been melted, just prior to its application.

After application, to adhere articles together, the reactive hot meltadhesive composition is subjected to conditions that will allow it tosolidify and cure to a composition that has an irreversible solid form.Solidification (setting) occurs when the liquid melt is subjected toroom temperature. Curing, i.e. chain extending, to a composition thathas an irreversible solid form, takes place in the presence of ambientmoisture.

As used herein, “irreversible solid form” means a solid form comprisingpolyurethane polymers extended from the aforementioned polyurethaneprepolymers. The composition having the irreversible solid formtypically can withstand temperatures of up to 150° C. Using a flameretardant the thermal stability of the irreversible solid can beimproved.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLES

In the Examples that follow, the following tests were used to determineviscosity and dynamic peel rate.

Viscosity:

Brookfield Viscometer with Thermosel heating unit, spindle 27

Dynamic Peel:

A 6 mil film of the adhesive was applied to a glass plate, preheated at120° C. A strip of vinyl (16 mm wide, 7 mil thick) with a hole punchednear one end was applied over the adhesive. The plate is inverted and,at several temperature intervals, a 103 g weight was applied to the holein the vinyl for 10–60 seconds. The peel rate at these intervals wascalculated.

Example 1

Reactive hot melt adhesives having the formulations shown in Table 1 (%by weight) were prepared. All the polyols and acrylic polymers (reactiveor not) were added to melt and mix under vacuum until homogeneous andfree of moisture. Then MDI was added and polymerization allowed toproceed with mixing under vacuum until reaction is complete. Theresulting pre-polymer was then placed into a container under a drynitrogen headspace to prevent exposure to moisture.

TABLE 1 Formulations of Reactive Hot Melt Adhesives With and WithoutMonoalcohols Sample A B C D Modaflow 0.6 0.6 0.6 0.6 PolyG 20-56 5.0 5.0PolyG 20-28 80.0 80.0 75.0 75.0 Elvacite 2902 5.0 5.0 5.0 5.0 Elvacite2967 45.0 45.0 45.0 45.0 Unilin 425 12.0 10.0 Unilin 350 8.0 MDI 15.017.3 17.5 17.7 DMDEE 0.15 0.16 0.16 0.32 ELVACITE 2902 (a 60,000 Mwacrylic - available from Lucite) ELVACITE 2967 (a 18,500 Mw acrylic -available from Lucite) MODAFLOW (an acrylic defoamer available fromSolutia) MDI PolyG 20-56 (a 2000 Mw polyether polyol available fromArch) PolyG 20-28 (a 4000 Mw polyether polyol available from Arch)UNILIN 425 (a 425 Mn polyethylene monoalcohol available from BakerPetrolites) UNILIN 350 (a 350 Mn polyethylene monoalcohol available fromBaker Petrolites)The results of testing on the formulas of Table 1 are illustrated inTable 2.

TABLE 2 Reactive Hot Melt Properties With and Without Monoalcohols A B CD Viscosity 1400 1700 (cps) 250° F. Viscosity 4575 5000 8175 (cps) 200°F. Melt Stability % 1.1 3.1 5.1 4.5 Dynamic Peel 20/26.0 0/37.0 2/26.98/29.1 Strength (mm/° C.)This data shows that high green strength reactive hot melts can beprepared using monoalcohols as crystalline monofunctional reactants. Thedata also shows that a formulation containing only polyether polyol andacrylics will give less green strength. The addition of the crystallinemonofunctional increased both the set speed and the green strength.

Example 2

Reactive hot melt adhesives were formulated according to-the process ofExample 1, however the formulations were prepared with and withoutmonoalcohols and with triol and/or multifunctional isocyanates. Theformulations are shown in Table 3.

TABLE 3 Reactive Hot Melt Formulations With and Without Monoalcohols andWith Triols and/or Multifunctional Isocyanates Sample E F G H Modaflow0.6 0.6 0.6 0.6 Acclaim 8200 15.0 PolyG 20-28 18.0 18.0 18.0 PolyG 30-422.0 2.0 Dianal BR-106 20.0 20.0 25.0 20.0 Elvacite 2967 40.0 40.0 40.040.0 Unilin 700 12.0 10.0 10.0 MDI 7.79 7.39 7.39 5.43 DMDEE 0.09 0.110.11 0.10 Mondur MR 3.54 4.0 4.12 3.72 ACCLAIM 8200 (8000 Mw low monolcontent polyether polyol from Bayer) PolyG 30-42 (3000 Mw polyethertriol from Arch) Dianal BR-106 (acrylic copolymer available from DaiAmerica) Unilin 700 (a 700 Mn polyethylene monoalcohol from BakerPetrolites) Mondur MR (polymeric isocyanate available from Bayer)The adhesive properties of samples E–H are shown in Table 4.

TABLE 4 Reactive Hot Melt Properties With and Without Monoalcohols andWith Triols and/or Multifunctional Isocyanates Sample E F G H Viscosity(cps) 10130 16500 28000 41200 275° F. Melt Stability % 0.7 0 0 1.0Dynamic Peel Strength 0/33.0 0/57.0 0/60.0 0/63.0 (mm/° C.)

Table 4 illustrates that reactive hot melt adhesives having a fast setspeed and high green strength may be prepared using monoalcohols andwithout polyester polyol.

Many modifications and variations of this invention can be made withoutdeparting from its spirit and scope, as will be apparent to thoseskilled in the art. The specific embodiments described herein areoffered by way of example only, and the invention is to be limited onlyby the terms of the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. A polyurethane hot melt adhesive composition consisting essentiallyof polyisocyanate, one or more polymeric polyols, a crystallinemonofunctional, polymeric reactant and a functional thermoplasticpolymer, wherein the one or more polymeric polyols is not a polyesterpolyol, wherein the adhesive comprises from about 5 wt % to about 20 wt% of the reactant and wherein the thermoplastic polymer is selected fromthe group comprising acrylic polymers, hydroxy functional acrylicpolymers, polyvinyl acetate, polyvinyl chloride, methylene polyvinylether, cellulose acetate, styrene acrylonitrile, amorphous polyolefin,thermoplastic urethane, polyacrylonitrile, polybutadiene, and mixturesthereof.
 2. The adhesive of claim 1, wherein the reactant is selectedfrom the group comprising hydroxyl reactants, carboxyl reactants, thiol,amine and mixtures thereof.
 3. The adhesive of claim 2, wherein thepolymeric polyol is a polyether polyol.
 4. The adhesive of claim 2,wherein the reactant is selected from the group comprising a lowmolecular weight linear polyethylene monoalcohol,polyethylene-block-polyethylene glycol, monol-terminated ring-openedpolyesters, monol-terminated ring-opened polyamides, or mixturesthereof.
 5. The adhesive of claim 4, wherein the reactant is a lowmolecular weight linear polyethylene monoalcohol.
 6. The adhesive ofclaim 2, further comprising plasticizers, compatible tackifiers, curingcatalysts, dissociation catalysts, fillers, anti-oxidants, pigments,adhesion promoters, stabilizers, aliphatic C₅–C₁₀ terpene oligomers,rosin, rosin derivatives, rosin ester, aliphatic hydrocarbons, aromatichydrocarbons aromatically modified aliphatic hydrocarbons, terpenes,terpene phenol, modified terpene, high molecular weight hinderedphenols, multifunctional phenols, sulfur-containing phenol,phosphorous-containing phenol, terpene oligomers, DMDEE, paraffin waxes,microcrystalline waxes, castor oil, hydrogenated castor oil, fireretardant additives, boron compound, aluminum hydroxide, antimonytrioxide, halogen compounds, halogen-containing phosphate compounds,tris(chloroethyl)phosphate, tris(2,3-dichloropropyl)-phosphate,ethylenebistetrabromophthalimlde, tris(2,3-dibromopropyl)-isocyanurateand mixtures thereof.
 7. A method of improving the set speed of apolyurethane adhesive comprising one or more polymeric polymeric polyolsthat are not a polyester polyol, comprising adding an effective amountof a crystalline monofunctional reactant to an adhesive formulation,wherein the adhesive comprises a functional thermoplastic polymer andwherein the adhesive comprises from about 5 to about 20 wt % of thereactant and the reactant is selected from the group comprising hydroxvlreactants, carboxyl reactants, and mixtures thereof.
 8. The adhesive ofclaim 7, wherein the thermoplastic polymer is selected from the groupcomprising acrylic polymers, functional acrylic polymers, hydroxyfunctional acrylic polymers, polyvinyl acetate, polyvinyl chloride,methylene polyvinyl ether, cellulose acetate, styrene acrylonitrile,amorphous polyolefin, thermoplastic urethane, polyacrylonhtrile,polybutadiene, isobutylene diol, and mixtures thereof.
 9. The method ofclaim 7, further comprising a polyether polyol.
 10. The method of claim7, wherein the reactant is selected from the group comprising a lowmolecular weight linear polyethylene monoalcohol, polyethylene-block -polyethylene glycol, monol-terminated ring-opened polyesters, ormixtures thereof.
 11. The method of claim 10, wherein the reactant is alow molecular weight polyethylene monoalcohol.
 12. A method of bondingmaterials together which comprises applying the reactive hot meltadhesive composition of claim 1 in a liquid form to a first substrate,bringing a second substrate in contact with the composition applied tothe first substrate, and subjecting the compositions to conditions whichwill allow the compositions to cool and cure to an irreversible solidform, the conditions comprising moisture.
 13. The method of claim 12,wherein the reactant is selected from the group comprising hydroxylreactants, carboxyl reactants, and mixtures thereof.
 14. The method ofclaim 13, wherein the reactant is selected from the group comprising alow molecular weight linear polyethylene monoalcohol,polyethylene-block-polyethylene-glycol, monol-terminated ring-openedpolyesters, or mixtures thereof.
 15. An article of manufacturecomprising the adhesive of claim 1.